The overall objectives of this work are to study the structure and assembly of oncornaviruses, specifically of Rous sarcoma virus, of a Rous-associated virus and of reticuloendotheliosis virus. Our goals include comparative studies on the number and location of polypeptides in these virions, including the minor components such as polymerase molecules. The method involves digesting virions with proteolytic enzymes to remove the surface glycoproteins; this permits the minor proteins to be displayed on polyacrylamide gels so they can be accurately quantitated. The nature of chloramine-T catalyzed surface iodination of enveloped viruses is under investigation. The structure of iodinated surface proteins will be examined to determine if the two polypeptides are separate or combined elements. Studies on the binding of cesium ions to rhinovirus 14 are being completed.